The present invention relates to a construction for and a method of waterproofing a wiring harness inserted through a tubular member such as a grommet.
In a motor vehicle, when a wiring harness is provided so as to pass through a panel separating an engine room and a cabin from each other, a grommet made of rubber is fitted into a through-hole formed on the panel and the wiring harness is inserted through the grommet such that penetration of water into the cabin is prevented.
The grommet is of substantially a shape of a frustum of cone and has a large diameter portion and a tubular portion extending from a reduced diameter end of the large diameter portion. Meanwhile, a panel mounting portion is provided on an outer peripheral surface of the large diameter portion of the grommet so as to be brought into engagement with an inner peripheral edge of the through-hole of the panel. A gap between the grommet and the through-hole of the panel is sealed positively so as to be waterproofed. Thus, the wiring harness is inserted from the tubular portion into the large diameter portion so as to be passed through the grommet.
If gaps exist among wires of the wiring harness passed through the grommet and between each of the wires and the tubular portion of the grommet, water may penetrate from the engine room into the cabin through these gaps. Therefore, these gaps are also required to be sealed.
Various waterproof constructions for sealing these gaps are known. For example, Japanese Utility Model Laid-Open Publication Nos. 1-66713 (1989) and 2-115221 (1990) disclose an arrangement in which pourable sealing compound is filled into the grommet from the large diameter portion so as to be penetrated into the gaps. Meanwhile, Japanese Utility Model Laid-Open Publication No. 4-23812 (1992) discloses an arrangement in which by employing an elastic cap having a plurality of holes for inserting the wires of the wiring harness therethrough, respectively, the elastic cap is fitted, in a state where the wires of the wiring harness have been, respectively, inserted through the holes of the elastic cap, into the tubular portion of the grommet and then, pourable sealing compound is filled from the large diameter portion up to inside of the elastic cap.
However, in the former known waterproof construction referred to above, unless the pourable sealing compound has a low viscosity of, for example, not more than 100 poise, the pourable sealing compound is less likely to penetrate into gaps among the wires. On the other hand, if viscosity of the pourable sealing compound is low, the pourable sealing compound may flow out of the gaps among the wires before being set. Therefore, in this known arrangement, it is impossible to perform complete waterproofing.
Meanwhile, in the latter known waterproof construction referred to above, gaps are positively formed among the wires. Thus, even if the pourable sealing compound has high viscosity, the pourable sealing compound readily penetrates into the gaps among the wires and thus, it is possible to perform complete waterproofing. However, in this known waterproof construction, the elastic cap is required to be provided additionally and its manufacture is troublesome due to addition of a step of inserting the wires through the holes of the elastic cap and a step of fitting the elastic cap into the grommet, thereby resulting in rise of its manufacturing cost. Furthermore, such a problem arises that diameter of the large diameter portion of the grommet is increased by the gaps among the wires, thus resulting in increase of size of the grommet.